1. Field of the Invention
The present invention relates to a yoke for a voice coil motor, VCM, incorporated within a recording disk drive such as a hard disk drive, HDD, for example.
2. Description of the Prior Art
A head actuator is incorporated within a hard disk drive. A voice coil motor of the head actuator includes a magnetic yoke. The yoke includes an upper yoke member and a lower yoke member coupled to each other. The lower yoke member is received on a first reference plane defined on a base of an enclosure. The upper yoke member is received on a second reference plane defined on bosses standing from the base. Screws are employed to couple the upper yoke member to the second reference plane. A voice coil is located in a space between the upper and lower yoke members. The voice coil is fixed to an actuator block capable of rotating around a support shaft.
Magnetic flux circulates through the upper and lower yoke members. The magnetic flux is generated in the voice coil in response to the supply of electric current. The interaction between the magnetic flux of the voice coil and the magnetic flux of the yokes causes the movement of the voice coil. The actuator block is thus allowed to rotate around the support shaft.
The alignment of the lower yoke member with the first reference plane in the aforementioned manner often hinders the contact of the upper yoke member against the second reference plane due to dimensional errors or the like, for example. The upper yoke member cannot be supported on the bosses. In this case, if the voice coil moves faster, the reaction of the yoke induces vibration of the yoke. The vibration deteriorates the accuracy in positioning a head slider coupled to the actuator block, for example. The vibration also causes the lower yoke member to contact the base. The contact makes noise.